Abstract
We have determined changes in thermal expansion coefficient alpha th and relaxation behavior of glassy materials by monitoring the first maximum of the diffraction pattern, obtained in transmission during in-situ heating in a high-intensity high-energy monochromatic light beam. The excess quenched-in free-volume Delta V-f and its relaxation kinetics can also be determined. Like metallic glasses, oxide glasses also show the glass transition T-g with excess free-volume trapped during cooling. The results allow quantitative determination of T-g by diffraction that compares well with T-g obtained by calorimetry as was previously reported for metallic glasses and the relaxation of excess free volume.